Thermal overload release device for contactors or automatic circuit breakers



Nov. 18, 1952 E. BESAG ETAL 6 8,7 0 THERMAL OVERLOAD RELEASE DEVICE FOR CONTACTORS OR AUTOMATIC CIRCUIT BREAKERS Filed July 11, 1950 2 SHEETS-SHEET l 1|" II AP La TL 1/ BIMETAL BIMETAL BlMETAL W @W WM 1 Nov. 18, 1952 E. BESAG ETAL 2,618,720 THERMAL OVERLOAD RELEASE DEVICE FOR CONTACTORS OR AUTOMATIC CIRCUIT BREAKERS Filed July 11, 1950 2 SHEETS--SHEET 2 F/G] W F768.

Qg'werixfors "(y w M,

A ltorneyS,

Patented Nov. 18, 1952 UNITED STATES 4* G F F [GE THERMAL OVERLOAD RELEASE DEVICE FOR CON TACTORS OR AUTOMATIC. CIRCUIT BREAKERS England Application July 11, 1950, .Serial No. 173,101 In Great Britain July 21, 1949 10 Claims. 1

This invention relates to improvements in and for contactors or automatic circuit breakers, and has for its principal object the provision of an improved construction for permitting the changing of the heater coils in an expeditious and simple manner while providing an eificient hearing for the movement of the bimetal element.

According to this invention, a heater coil and a conductor strip or strips are carried on an insulating plate adapted to be centralised by means constituting the pivot mounting for the bimetal. Such means for pivotally mounting the bimetal may be in the form of an upstanding pin on which a tube, secured to a bracket on the bimetal, is rotationally mounted, the upper end of the pin projecting beyond the tube being insertible in a deep recess formed in the insulating plate which carries the heater coil and conductor strip or strips. The conducting strip or strips secured to this plate may be connected, as by welding or brazing, to respective ends of the heater coil and are adapted for ready disconnection from terminals at the front of the circuit breaker. The improvements of the present invention provide a simple arrangement for facilitating changing and replacement of heater coils when coils of different ratings are required. The extended engagement of the tube with the pin provides an effective rotational pivot for the bimetal.

In order to enable the invention to be readily understood, reference will now be made to the accompanying drawings, illustrating by way of example one construction for carrying the present invention into effect, and showing the same when used in connect-ion with an overload release box for a motor starting switch, inwhich drawings:

Figure 1 is a plan view.

Figure 2 is a plan view with the cover and other parts of the box removed.

Figure 3 is a perspective view of a heater and bimetal disassembled.

Figure 4 is a perspective view from a different angle than that of Figure 3, of the heater of our present invention.

Figure 5 is a section on the line V- V of Figure 2.

Figure 6 is an inverted plan view of a modified heater.

Figure '7 is a side elevation of the modified form of heater shown in Figure 6, and

Figure 8 is a side elevation of another modified form of heater.

Referring to the drawings, three thermal re-' lease devices a are mounted-in the intermediate chambers b 'of an overload box 0 of anautomatic circuit breaker, the end chambers .11; e, housing trip mechanism 1 and ambient adjustment means g respectively. In the rear of the box are disposedtrip bars h, h of the construction described and claimed in U. S." Patent No. 2,527,907 dated October 31", 1950," and in the front of said box are the main'terminals i and contacts is one only of which is shown Figure 1. The'trip mechanism may be'ofthe construction described and claimed in U. S. Pat- 1950.- Each release device acomprises a bimetal strip k bent to substantially cylindrical form;

one endbeing ext-ended outwards at k for engagement with a trip'bar h,- and the other end, which is flattened, being attached by eyelets Z to the middle limb of a Z-shaped bracket m; Each bimetal is disposed around'a heatercoil n and has its longitudinal axis vertically arranged as viewed inFigure 5. One of the outer limbs m of the bracket is disposed underneath the bimetal and has an upwardly extending tube 0 secured to it'by riveting. The other horizontal limb m of the bracket-m is extended outwardly and its rounded end isengaged by the co-ordinating member h of the-trip bars of the automatic circuit breaker. The tube 0 is fitted over a pin :0, which pin has a drive fit in a recess in the bottom 0 of the insulating box. The box is provided with a cover 1' having three openings r for permitting access to the heater coils, and each opening is closed by an insulating plate w. The pin 1;) protrudes beyond the upper end of the tube 0, and a split ring s thereon prevents inadvertent upward movement of the tube 0 on the pin 12.

Each heater coil n is bent from a strip to form almost a complete cylinder, and each of its ends, disposed to the rear of the chamber b, is welded to a conducting strip or connector t, the other end of which strip is adapted to be detachably connected to a terminal u, u at the front of the box. Each of these strips 15 is of inverted U shape, the vertical arm a being welded tothe heater n, while the horizontal arm is disposedover the bimetal k and heater n and being secured by rivets c to the front edge of the insulating cover plate w. Each strip t projects forwardly beyond the cover plate w and has a depending bifurcation 2L3 adapted for readily removable connection with a terminal a, u One of these terminals u is connected to a main fixed contact k, by a strip an, attached by screws to the contactor casing. The other terminal u is connected by another strip .12 to a main wiring terminal i on the front of the casing.

Each insulating cover or closure plate to is adapted to close a correspondingly shaped aperture in the cover r and is formed with grooves or channels for receiving the horizontal arms u of the connector strip 15, and has a central depending spigot w which is formed with a deep recess w adapted to fit closely over the upper end of the pin p which projects above the bimetal is, thereby correctly locating the closure plate w and, with it, the connector strips t and coil n in proper relation to the bimetal k The disposition below the bimetal k of the bracket limb m which supports the tube 0, enables the removal and replacement of heater coils n from above.

According to a modified construction (see Figures 6, 7 and 8) for smaller current ratings, the heater is in the form of wire 9 coiled around the outside of an asbestos tube 2 which is disposed around, and depends from, a central stem 3 of an insulating plate 20. l are welded to short connector strips 12 which have their rear ends t terminating a short distance from the front of the insulating plate w.

The insulating plate 112 may have inscribed or otherwise applied to its top surface, in addition to the numerical rating in amperes of the heater coil, indicator markings, as shown applied to the left hand unit, Figure 1, these markings corresponding with similar markings on the knob of the adjustable cam 4 of the ambient adjustment means g, which means may be of the construction described and claimed in the specification of U. S. Patent No. 2,606,062, dated August 5, 1952, For example, each plate 10 may have inscribed or otherwise applied to its top surface five numeral markings and five corresponding alphabetical indications, and the knob which controls the earn 4 of the adjustment means may bear similar indications. Thus any series of plates w may be used for five ratings, the same adjustment of 1. A thermal overload release device for motor starting switches including an overload box having contacts thereon and trip mechanism therein, an insulating plate adapted to overlie a chamber in said overload box, a substantially cylindrical heater coil secured to and depending from the underside of said insulating plate and disposed within said chamber in said overload box, conductor strips connected to said heater coil adapted for attachment to the contacts on said overload box, a substantially cylindrical bimetal member for actuating the trip mechanism in said overload box, said bimetal member being disposed within said chamber in said overload box and adjacent said heater coil, and means for removably mounting said bimetal member within said chamber in said overload box for pivotal movement about its axis, said means engaging said insulating plate to maintain said heating coil in substantially concentric relation with respect to said bimetal member.

2. A thermal overload release device for motor starting switches as defined in claim 1, wherein the conductor strips are secured to the underside of said insulating plate and connect said heater coil to said insulating plate.

The ends of the wire 1 iii 3. A thermal overload release device for motor starting switches as defined in claim 1, wherein said substantially cylindrical heater coil is 01 greater diameter than said substantially cylindrical bimetal member, and surrounds said bimetal member in said chamber.

4. A thermal overload release device for motor starting switches as defined in claim 1, wherein the means for removably mounting the bimetal member within said chamber and for maintaining said heating coil in substantially concentric relation with respect to said bimetal member comprises a vertical pin extending upwardly from the wall defining the bottom of the chamber in the overload box and means secured to said bimetal member and rotationally mounted on said pin, the upper end of said pin extending beyond the upper end of said bimetal member and into a recess in the underside of said insulating plate.

5. A thermal overload release device for motor starting switches as defined in claim 4, wherein the means secured to the bimetal member and rotationally mounted on the pin comprises a tube.

6. A thermal overload release device for motor starting switches as defined in claim 1, wherein each conductor strip connected to the heater coil is provided with a terminal adapted for ready connection to, and disconnection from, the contacts on the overload box.

'7. A thermal overload release device for motor starting switches including an overload box having contacts thereon and trip mechanism therein, an insulating plate adatped to overlie a chamber in said overload box, a substantially cylindrical heater coil secured to and depending from the underside of said insulating plate and disposed within said chamber in said overload box, conductor strips connected to said heater coil adapted for attachment to the contacts on said overload box, a longitudinally-split, substantially cylindrical bimetal member for actuating the trip mechanism in said overload box, said bimetal member being disposed within said chamber in said overload box and adjacent said heater coil with the walls defining the longitudinal split in relatively close, spaced relation, a bracket secured to said bimetal member and having an inwardly extending portion, and a vertical pin extending upwardly from the wall defining the bottom of the chamber in the overload box and passing through an aperture in the inwardly extending portion of said bracket whereby said bimetal member is mounted for pivotal movement about said pin, said pin extending upwardly beyond the top of the bimetal member and into a recess in the underside of said insulating plate to maintain said heating coil in substantially concentric relation with respect to said bimetal member.

8. A thermal overload release device for motor starting switches as defined in claim 7, wherein the inwardly extending portion of said bracket has secured thereto a vertically extending tube rotationally mounted on the vertical pin.

9. A thermal overload release device for motor starting switches as defined in claim '7, wherein the bracket is of substantially Z-shaped formation, with the vertical, intermediate portion of said bracket secured to the bimetal member, the upper horizontal portion adapted to contact the trip mechanism of the overload box, and the lower horizontal portion having an aperture therein for surrounding the pin to rotationally mount said bimetal member on said pin.

10. A thermal overload release device for motor starting switches as defined in claim 9, wherein 2,818,720 5 a tube is secured within the aperture in the lower horizontal portion of the bracket and surrounds Number sald pm.

1,987,717 ERNST BESAG. 2,337,084

THOMAS DANIEL GUY WINTLE. 5 2 407 743 REFERENCES CITED 2,523,897

The following references are of record in the file of this patent:

6 UNITED STATES PATENTS Name Date Smith Jan. 15, 1935 Crise Dec. 21, 1943 Helyar Sept. 17, 1946 Besag et a1 Sept. 26, 1950 

